add explicit API to know if the writebuffer is using its external storage

To help with https://skia-review.googlesource.com/c/skia/+/114262

Bug: skia:
Change-Id: I83fcccdec0dbaef28d0e557ea6fb9bd0ed59ed44
Reviewed-on: https://skia-review.googlesource.com/114284
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/core/SkWriter32.h b/src/core/SkWriter32.h
index e81178d47e..1e004a8b1d 100644
--- a/src/core/SkWriter32.h
+++ b/src/core/SkWriter32.h
@@ -39,6 +39,10 @@ public:
     // return the current offset (will always be a multiple of 4)
     size_t bytesWritten() const { return fUsed; }
 
+    // Returns true iff all of the bytes written so far are stored in the initial storage
+    // buffer provided in the constructor or the most recent call to reset.
+    bool usingInitialStorage() const { return fData == fExternal; }
+
     SK_ATTR_DEPRECATED("use bytesWritten")
     size_t size() const { return this->bytesWritten(); }